He’s been doing this for 20 years. Here’s how he describes his sand paintings:

These Guerrilla style installations, above and below the tidal zones of some of the most exposed coastal locations in the land, are purely ephemeral, and may be gone within a few waves, a tide or a storm, deliberately made to disappear.

Watch him make one:

He doesn’t only work with sand. His other works might be “as simple as coloured water, a track through snow, or a group of painted rocks — left to nature and passersby.”